It is typical to get up to several inches (at 100 yards) of zero shift when a suppressor is mounted. If you get more than a foot, there is something mechanically wrong. The most likely thing is that the suppressor bore is not aligned and true to the barrel bore, and even if there are not visible bullet strikes, the path could be too close or it could just be "grazing" something in the suppressor. If you remove the bolt, mount the suppressor, and look down the barrel from the breech end, you should see a shadow of the front endcap of the suppressor and it should be a perfectly circular shadow, centered about the bore. If it is off to one side, then you can tell it is not aligned right.

It could be a problem with just the suppressor, or it could be a problem with the barrel(s) and thread/shoulders, and maybe the accurate suppressor just doesn't expose the problem. Ideally, AWC should be able to figure out exactly what's wrong if they had the barrel and suppressor, but they should be able to check just the suppressor.